The subject matter of the present invention relates to an apparatus for preventing a back fired detonation wave from propagating through a detonating cord, and more particularly, to an explosive diode transfer system for use in a modular perforating apparatus for preventing a back fired detonation wave originating from a lower oriented gun of the modular perforating apparatus from detonating a higher oriented gun in the perforating apparatus.
In a modular perforating apparatus, a plurality of perforating guns are serially connected together including a first, higher oriented perforating gun, a second, lower-oriented perforating gun connected to the first perforating gun and located below the first perforating gun when disposed in a borehole, and possibly additional perforating guns connected to the second perforating gun and located below the second perforating gun when disposed in a borehole. Normally, one firing head is located at the top of the gun string, a detonation of the firing head serially detonating the perforating guns of the modular perforating apparatus starting with the first higher oriented perforating gun. For safety reasons, the one firing head is connected to the top of the gun string after the modular perforating apparatus has been lowered into the borehole; and, following detonation of the perforating apparatus, the firing head is the first to be removed. However, if the firing head fails to detonate, the perforating apparatus disposed in the borehole is not detonated. Therefore, in order to improve the reliability of the modular perforating apparatus, a firing head is associated with each perforating gun of the modular perforating apparatus. As a result, if the firing head associated with the higher oriented perforating gun fails to detonate, the firing head associated with the lower oriented gun may be detonated. However, with this configuration, the safety issue is adversely affected. Since each perforating gun now has its own firing head, the gun string, including the firing heads, must be assembled at the surface of the borehole prior to lowering the perforating apparatus into the borehole. If one firing head accidentally detonates, an unwanted detonation of the perforating apparatus may occur. In particular, a detonation wave originating from a lower oriented perforating gun of the modular perforating apparatus may propagate in two directions, that is, in a downward direction and in an upward direction. A detonation wave which originates from the lower oriented perforating gun and which propagates within the detonating cord in the upward direction is known as a backfired detonation wave. A back-fired detonation wave originating from the lower-oriented perforating gun may cause an unwanted detonation of a higher-oriented perforating gun of the modular perforating apparatus. Consequently, for safety reasons, an apparatus is needed, which is adapted to be interconnected between adjacent perforating guns of the modular perforating apparatus, for preventing a back-fired detonation wave originating from the lower-oriented perforating gun from detonating the higher-oriented perforating guns of the modular perforating apparatus.